Scratching my head trying to understand how it's possible that a mastered track, limited to 0 dBFs, can still peak over 0 dB on the channel and master fader. This is happening both in Ableton and Logic, both with all plugins disabled and without any. Also, track is not warped. Any ideas?

Last edited by noceur on Fri May 20, 2016 3:05 pm, edited 3 times in total.

tbh, i don't know what it's limited to. these are commercial releases i am looking at, with some peaking over 1-2 db. I think the answer is use of a limiter that is not a true peak (intersample peak) limiter.

1. as already mentioned, there are the physics of intersample peaks. many limiters only block the highest samples from being over 0dB. But since the actual analogue signal is a curve that can rise above two sampling points, there might be higher peaks.

2. since lossy conversions definitely alter the actual stored data (you might not be able to hear it, these codecs have become very good even in medium high settings and are often indistinguishable even for professionals on professional systems), there might be changes to the highest peaks as well. so you better leave a headroom of 1dB from your master file. that should be fine.

The decoding of the mp3s is the issue. Often times that leads to peaks that weren't in the original signal, the joys of compressed audio files.

Isn't this a mastering error? And a reason some mastering houses deliver also the MP3 as well as lossless?

No, because the mastering engineer usually has no control over what MP3 algorithm will be used to make the compressed file. Even if we make it ourselves, you might need to lower the output 2-3dB to prevent clipping. Another reason I like AAC over MP3, with the mastered for iTunes tools you can make sure you're not clipping anywhere later on.

Though I will admit, unless you're going to be doing more production with the MP3 later on (and why would you not use the wav?), I personally wouldn't stress too much about this post conversion clipping. Pretty much all MP3s have it, and no one is up in arms about it to date.